Building Extractable Libraries in Rails - DCRUG

version 2.0 of the slidedeck presented for DCRUG on 7/12/2012

Transcript

1. Building Extractable Libraries in Rails
2. Hello There! I’m @patricksroberts. I work at @iorahealth. I co-organize @bostonrb. I maintain @copycopter.
3. I’m not so secretly using you for a sailing vacation.
4. The Duality of a Rails Developer
5. Ruby is driven by <3
6. Our best practices change with our sense of beauty
7. Our ecosystem is driven by the many ways to solve problems
8. Rails is driven by Conventions
9. Rails frees us from making many tedious decisions
10. The freedom from decisions allows us unparalleled productivity
11. /lib is a Battlefield
12. I think it can benefit from some conventions So we can ship some more code
13. Avoid the Autoload Trap Maintain explicit entry points into your library code using initializers
14. Use the Configuration Pattern Keep credentials as far away from your library code as possible
15. Isolate Interaction with your Domain Models Use the DCI pattern at the glue points of your application code
16. Avoiding the Autoload Trap
17. Rails 3 brought a wonderful convention for removing /lib from automatically being loaded on application boot...
18. ... however our first instinct is to do this: # config/application.rb # Custom directories with classes and modules you want to be autoloadable. config.autoload_paths += %W(#{config.root}/lib) Let’s try something different!
19. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ # lib/twitter_wrangler.rb require ‘twitter_wrangler/authentication’ require ‘twitter_wrangler/authorization’ module TwitterWrangler end Combined with...
20. We have created a namespace and setup a proper layout when we need to extract our code outside the application into a gem. ... in ten seconds or less :)
21. Hide Your Credentials From Your Library
22. It’s so simple to do this: # lib/twitter_wrangler.rb module TwitterWrangler OAUTH_KEY = ‘ABCDEFG1234ZXYZB2324’ end Or even this: # lib/twitter_wrangler.rb module TwitterWrangler OAUTH_KEY = ENV[‘TWITTER_KEY’] end
23. But we already have an entry point for our library code. So let’s exploit the heck out of it!
24. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end
25. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end
26. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end
27. # config/initializers/twitter_wrangler.rb require_relative ‘../lib/twitter_wrangler’ TwitterWrangler.configure do |config| config.oauth_key = ENV[:twitter_oauth_key] end
28. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
29. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
30. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
31. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
32. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
33. # lib/twitter_wrangler/configuration.rb module TwitterWrangler class Configuration attr_accessor :oauth_key def initialize self.oauth_key = nil end end class << self attr_accessor :configuration end def self.configure self.configuration ||= Configuration.new yield(configuration) if block_given? end end
34. With one additional, boilerplate class we’ve established a separation of credential concerns
35. Keeping Your Domain Models Focused
36. Prescriptions Queueing Authorization Authentication Timeouts Caching BMI Appointments
37. Web App body mass index tweet called Library Authorization Twitter message Authentication Queueing
38. # lib/twitter_wrangler/roles/tweeting_patient.rb module TwitterWrangler::Roles::TweetingPatient def bmi_twitter_message “Today my BMI is #{body_mass_index} and I’m #{percent_of_body_mass_index_goal} from my goal of #{body_mass_index_goal}!” end end
39. # lib/twitter_wrangler/support/fake_patient.rb class FakePatient def body_mass_index;27;end def percent_of_body_mass_index_goal;”95%”;end def body_mass_index_goal;25;end end # spec/twitter_wrangler/roles/tweeting_patient_spec.rb describe TweetingPatient do let(:patient) { FakePatient.new } before { FakePatient.extend TweetingPatient } it ‘asserts some fantastic things’ do #GLORIOUS SPECS end end
40. # spec/twitter_wrangler/roles/tweeting_patient_spec.rb describe TweetingPatient do let(:patient) { mock() } before do patient.stubs({body_mass_index: 27, percent_of_body_mass_index_goal: “95%” body_mass_index_goal: 25 }) patient.extend TweetingPatient end it ‘asserts some fantastic things’ do #GLORIOUS SPECS end end
41. # lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_reader: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end
42. # lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_reader: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end
43. # lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_reader: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end
44. # lib/twitter_wrangler/Contexts/BMITwitterUpdate.rb module TwitterWrangler::Contexts class BMITwitterUpdate attr_reader: patient def initialize(patient) @patient = patient @patient.extend TweetingPatient end def call TwitterWranglerQueue.add @patient.bmi_twitter_message end end end
45. # spec/models/patient_bmi_observer_spec.rb describe PatientBMIObserver do let(:bmi_update) { mock() } before do BMITwitterUpdate.stubs(:new).returns bmi_update bmi_update.stubs :call end it ‘sends a twitter update on mah BMI’ do # expect #call to have been called once end end
46. # spec/models/patient_bmi_observer_spec.rb describe PatientBMIObserver do let(:bmi_update) { mock() } before do BMITwitterUpdate.stubs(:new).returns bmi_update bmi_update.stubs :call end it ‘sends a twitter update on mah BMI’ do # expect #call to have been called once end end
47. Provides clear separation of Domain Model and outside code Creates isolatable tests Easy path forward for gem extraction Boilerplate :( YAGNI :(
48. Thanks!
49. Questions? I only take questions in the form of answers OR in haiku